1. Field of the Invention
The present invention relates to an electronic device, a communication system, a method of communication, and a program having or involving a one-directional high-speed communication interface that can transmit pixel data of uncompressed video, such as the High Definition Multimedia Interface (HDMI), for example.
2. Description of the Related Art
According to the HDMI specification, a device functioning as a transmitter device is referred to as an HDMI Source (device), and hereinafter, also referred to as a Source (device); and a device functioning as a receiver device is referred to as an HDMI Sink (device), and hereinafter, also referred to as a Sink (device).
An HDMI Source and an HDMI Sink each have an HDMI connector for connecting an HDMI cable that includes a plurality of signal lines. The HDMI connector is a connector used for transmitting a digital signal of audio and video data.
The specification for HDMI defines the Transition Minimized Differential Signaling (TMDS) channels used for high-speed one-directional transmission of audio and video data from an HDMI Source to an HDMI Sink and the Consumer Electronics Control (CEC) line used for bidirectional communication between an HDMI Source and an HDMI Sink, etc.
In recent years, HDMI has been increasingly used as a high-speed communication interface for transmitting a digital television signal, i.e., pixel data of uncompressed (baseband) video and the accompanying audio data, from audio visual (AV) sources such as a digital versatile disc (DVD) recorder and a set-top box to displays such as a TV receiver (TV) and a projector.
Today, DVD players have an HDMI output port, and TVs or the like have an HDMI input port.
Also, the number of personal computers (PCs) and home camcorders having an HDMI output port for connection to a TV has increased.
CEC is an optional specification within the HDMI specification defined on the basis of P50, which has widely been used in Europe. CEC is a protocol defining a method of bidirectional serial communication that uses one signal line within an HDMI cable.
The data transfer rate of CEC is a low 416 bps (theoretical). CEC has a feature that, by using CEC, devices connected with an HDMI cable can take a form of connection via a bus in a multi-master mode, which allows either device to become an initiator (master) or a follower (slave).
As an example of using CEC, assume a state in which a video player (Source) is connected to a TV (Sink) using HDMI. When the TV is switched off by a remote control of the TV, information regarding the switching off of the TV is transmitted from the TV to the video player via CEC, and both the TV and video player can be simultaneously switched off.
Another example is that depressing a play button of a video player allows simultaneous switching of the input mode of a TV to select a video channel.
These functions allow a user to operate a TV and a video player without having to change a remote control for another.
CEC has a feature that it is the only protocol of proactively transmitting data from a Sink to a Source, in an HDMI system where data is transmitted in one direction from a Source to a Sink. Hence, CEC provides a communication line that allows a TV to transmit data proactively.
Japanese Unexamined Patent Application Publication No. 2007-006298 has disclosed an example where CEC can be used as an auxiliary method for signal transmission between systems connected by HDMI. CEC, which can send and receive information among systems having HDMI connections, is expected to be used in a wider area of applications.